KR20060027351A - Raising detectability of additional data in a media signal having few frequency components - Google Patents

Abstract

The present invention relates to a methods, devices, a media signal as well as an information storage medium related to embedding additional data in a media signal. A first adding unit (12) mixes the media signal (x) with a noise signal (n) in order to provide a modified media signal (x + n), and a combiner unit (14) combines additional data (w) with the modified media signal (x + n) through multiplying the modified media signal with the additional data in order to provide a host modifying media signal (mw). In this way the additional data can be detected with a higher certainty in an output signal (y) if the media signal (x) includes few frequency components.

Description

Raising detectability of additional data in a media signal having few frequency components

The present invention generally relates to the field of providing additional data in a media signal, and more particularly to methods, devices, signals and information storage media related to embedding of additional data in a media signal.

With the development of the Internet, virtually unlimited amounts of information content can be accessed or retrieved. In this case, the content may be provided in the form of media signals changing shapes and shapes by different content providers. The media signals may be provided, for example, as audio signals in a compressed or decompressed form, image signals in a compressed or decompressed form, and video signals in a compressed or decompressed form. In order to prevent the media content from being illegally obtained or illegal copying of content by people who are not entitled to the media content, content owners need to protect their content. To protect the content, they often need to provide additional information in the media signals. Additional information may also be provided for other reasons, such as providing text with respect to audio (eg, lyric).

One field of use in which additional data is provided within a media signal is the field of Digital Rights Management (DRM), where additional data in the form of watermarks may be used to prevent media content from being tampered with. Used to indicate possible sources of users.

The possibility of accurate and effective watermark detection is highly dependent on the data embedding method into the host signal and the characteristics of the host signal. One form often used for embedding watermarks is called multiplicative watermarking, where the media signal to be watermarked is multiplied with the corresponding watermark. On the other hand, in general, a media signal has many different frequency components, and may sometimes have fewer frequency components. In the case of low frequency components, it may be difficult to detect embedded watermarks using multiplication watermarking.

International Patent Application No. WO-A-02 / 15587 describes a method in which additional data, such as a watermark, is added to a media signal. Here the signal is described with respect to a sine wave. The binary code is added to the signal of the high frequency band by adding or not adding noise to the high frequency band. Upon detection, the sequence of acquired digits (ie, 0s and 1s) represents watermark information (coded version of). Thus, the document describes a technique for additive watermarking, which is not applicable to multiplicative watermarking environments. In addition, since additional information is provided only within the high frequency band (which can be easily filtered using a simple low band filter), when robustness is an important condition, addition watermarking is brittle and therefore unsuitable.

In a more robust multiplication watermarking method, circularly shifted chip sequences of a plurality of real numbers are multiplied with an appropriately scaled version of the media signal and added back to the original media signal. Upon detection, the distances between the various correlation peaks carry watermark information (coded version of). If the host signal contains less frequency components, the correlation will be weak. Thus, there is a need to further increase the detectability for additional data that is embedded using a multiplication embedding technique for media signals having fewer frequency components.

It is therefore an object of the present invention to provide a robust multiply embedding method of embedding additional data in a section of a media signal, in particular a section of a media signal with less frequency components.

According to a first aspect of the invention, there is provided a method for embedding additional data in a media signal:

Obtaining a media signal;

Mixing at least one section of the media signal with a noise signal to provide a modified media signal; And

The object of the invention is achieved by an embedding method comprising combining said additional data with said modified media signal to provide a first host altered media signal.

According to a second aspect of the invention, there is provided a device for embedding additional data in a media signal:

A first adding unit for mixing at least one section of the media signal with a noise signal to provide a modified media signal; And

The object of the invention is also achieved by an embedding device comprising a combiner unit for combining the additional data with the modified media signal to provide a first host altered media signal.

According to a third aspect of the invention, as a media signal:

The object of the present invention is also achieved by a media signal comprising at least one section of an altered media signal comprising a media signal mixed with a noise signal, wherein additional data is combined with the altered media signal.

According to a fourth aspect of the invention, as an information storage medium:

An object of the present invention is also achieved by an information storage medium comprising a media signal comprising at least one section of an altered media signal comprising a media signal mixed with a noise signal, wherein additional data is combined with the altered media. do.

The present invention also relates to providing a technique for (automatically) switching between a media signal and a modified version of the media signal to selectively improve the detectability of embedded information in multiplication with this new host signal.

According to a fifth aspect of the invention, there is provided a method for embedding additional data in a media signal:

Obtaining a media signal;

Analyzing the media signal;

Mixing at least one section of the media signal with a noise signal to provide a modified media signal; And

For different sections of the media signal, the object of the invention is also achieved by an embedding method, comprising combining the additional data with the modified media signal or the original media signal, depending on the analysis. .

According to a sixth aspect of the invention, there is provided a device for embedding additional data in a media signal:

A first adding unit for mixing at least one section of the media signal with a noise signal to provide a modified media signal;

A combiner unit for combining the additional data with the modified media signal or the media signal to provide a first host altered media signal; And

An analysis unit arranged to analyze the media signal and to control, for different sections of the media signal, providing the modified media signal or the media signal to the combiner unit depending on the analysis. The object of the present invention is also achieved by.

Claims 2 and 16 relate to performing the combination using multiplication.

Claims 5 and 17 relate to shaping a noise signal based on a human perceptual model.

Claims 6 and 18 relate to shaping a modified media signal combined with said additional data with a signal shaping function based on a human perceptual model.

Claims 8, 9, 10, 20, 21 and 22 scale the added noise, add the media signal to the modified media signal combined with the added data, and not scale to the media signal combined with the additional data. It is about adding a noisy signal. This has the advantage of providing a more predictable control mechanism for the purchase of additional data.

Claims 12 and 23 relate to analyzing a media signal and combining sections of media signal or media signal mixed with noise depending on the analysis with additional data.

The present invention provides better detection possibilities of additional data when embedding additional data in media signals having less frequency components, for example, high tone signals such as pitch-pipe or harpsichord excerpts. This has the advantage. With the present invention, it is possible to embed a more easily detectable watermark in a modified media signal, for example, compared to a general media signal having these characteristics. Due to this higher level of detectability, even if the quality of the media signal is degraded, the additional data is still detectable, i.e. the probability of accurate detection is increased. At this point, for example, rhetorical tracking of the processed media signal is facilitated.

Thus, the general idea of the present invention is to mix the media signal with the noise signal and to combine additional data with the media signal, which is changed in this way.

These and other features of the present invention will be apparent from the embodiments described hereinafter, and will be described with reference to the embodiments.

1 is a schematic diagram of a device for embedding a watermark into a modified media signal according to a first embodiment of the present invention;

2 is a schematic representation of a first variation of a combiner unit that may be used in the device of FIG. 1.

3 is a schematic representation of a second variation of a combiner unit that may be used in the device of FIG. 1.

4 is a schematic diagram of a device for embedding a watermark into a modified media signal in accordance with a second embodiment of the present invention;

5 is a schematic diagram of a device for embedding a watermark into a modified media signal according to a third embodiment of the present invention.

6 is a flowchart of a method for embedding a watermark into a modified media signal according to a third embodiment of the present invention.

7 is a schematic diagram of a device for embedding a watermark into a modified media signal according to a fourth embodiment of the present invention.

8 is a schematic diagram of a device for switching between embedding of a watermark in an original media signal or a modified media signal in accordance with the present invention;

9 is an information storage medium in the form of a CD disk having a media signal stored on the information storage medium according to the present invention.

The invention will be explained in more detail with reference to the accompanying drawings.

The present invention relates to the field of providing additional data in media signals having sparse frequency content in at least some of the media signal. In the audio field, such signals may include sound from instruments such as harpsichord and pitch pipe. However, the present invention is not limited to audio and can be applied to other media signals such as, for example, video or digital images. The additional data is preferably provided in the form of a watermark. However, it is noted that the present invention is not limited to watermarks, and that the additional data may be any additional data that needs to be detected within the media signal, such as additional text associated with the song. Should be.

1 shows a schematic diagram of a device 10 for embedding additional data in a media signal having sparse frequency content according to a first embodiment of the present invention. For this reason, the device 10 comprises a first adding unit 12, which firstly receives the media signal x and makes noise to provide the modified media signal x + n. Add signal n. The media signal x is often referred to as the host signal in these situations. The modified host signal x + n is then provided to the watermark combiner unit 14, which combines an additional in the form of a watermark _w to provide a first host change signal m _w at its output. Combine the data. Finally, in the second adding unit 36, the first host change signal m _w is changed to provide the additional signal to the output media signal y, or the host signal x + n (or the host signal ( x)) is added again. The combiner unit 14 shown here is a filter that applies a watermark in the form of suitably selected filter coefficients. Therefore, the combiner unit 14 is a multiplication unit for changing the changed host signal (x + n) by multiplying the host signal and the watermark. Since the altered signal contains more frequency components than the original signal, the watermark is more easily detected. The noise signal n is an additional watermark carrier, where both the noise signal and the host signal carry a watermark.

However, signals with many different frequency components can also benefit from this type of embedding, especially by the insertion of shaped noise in the higher frequency region. This will not significantly improve the robustness of the watermark, but for unprocessed and unwatermarked audio, this can yield significantly better detection reliability.

2 shows a first variation of combiner unit 14 according to the invention, the combiner unit operating in the frequency domain. Thus, the combiner unit comprises a discrete Fourier transform unit 16 which receives the modified host signal x and converts it into the frequency domain. The converted and modified host signal is then provided to the multiplication unit 18, which multiplies the converted and changed host signal with the watermark w. Here, the watermark w is a frequency domain watermark. The watermarked, transformed and modified host signal is then provided to the Fourier inverse transform unit 20, and the Fourier inverse transform unit converts the watermarked, transformed and modified host signal back into the time domain, and provides it to the multiplication unit 22. . Multiplication unit 22 also receives the results from the increase / decrease on / off switching function. Thus, to provide this switching, the modified host signal x + n is provided to unit 24, which uses a temporal gain function G. The output of multiplication unit 22 is then provided to scaling unit 26, which scales the multiplied signal by the scaling parameter α. This multiplied and scaled signal is then provided to a second adding unit 36, which adds these signals together to receive a modified host signal and form an output signal y, the output signal being It is a watermarked host signal. The purchase of watermarks according to this principle was carried out by Michiel van der Veen, Fons Breukers, Jaap Haitsma, Ton Kalker, Aweke Negash Lemma and Werner Oomen in May 2001, Proceeding of the 110th AES Convention, Amsterdam, The Netherlands. multi-functional and high-quality audio watermarking technology ".

The frequency domain combiner unit described above can be modified in many ways. For example, it is possible to remove the branch containing the amplification unit and also to remove the scaling unit, but this will degrade the signal quality.

3 shows another variation of the combiner unit operating in the time domain. The combiner unit 14 comprises a band pass filter 30, the band pass filter filters the modified host signal x + n, provides the filtered signal to the multiplication unit 32, and the multiplication unit is also provided. A watermark is received and multiplied by the watermark and the filtered modified host signal (x + n). The output of the multiplication unit 32 is connected to the scaling unit 34, which scales the watermarked signal with the scaling parameter α and provides it to the second adding unit 36, which adds also to the addition unit. Receive the changed host signal (x + n). At this time, the output of the second adding unit 36 is the watermarked host signal y. The scaling unit 34 here is not necessarily required to provide a watermarked signal. Here, the watermark w is a time domain watermark. This watermarking technique is described by IEEE Transaction on Signal Processing, April 2003, Vol 51, pp. 1088-1097, Aweke Negash Lemma, Javier Aprea, Werner Oomen and Leon van de Kerkhof, incorporated herein by reference. temporal domain audio watermarking technique.

The combiner units described above are merely examples of multiplier combiner units rather than used in the present invention. Many other types of multiplication combiner units may be used instead.

The watermarking technique shown and described in FIG. 1 can be improved, in which a human perceptual model can be used to shape a noisy signal to reduce perceptible distortion. The model used depends on the type of signal. In the case where the media signal is an audio signal, the model is a psychoacoustic model of the human listening system, and when pure images are used, the psych-visual model of the human visual system is used. .

A schematic diagram of a device for embedding a watermark in a media signal according to the second embodiment of the present invention is shown in FIG. The device of FIG. 4 basically comprises the same components as the device of FIG. 1. The difference is that the device 10 further comprises a first signal shaping unit 40 and a filter control unit 38 in the form of a masking filter. The filter control unit 38 receives the host signal x and analyzes this signal using a psychoacoustic model of the human auditory system P. The unit 38 uses the results from the analysis to select filter coefficients of the filter 40. The filter 40 receiving the noise signal n shapes the noise using the first signal shaping function M1 so that the shaped noise signal n _s is obtained. This shaped noise signal n _s is then provided to the first adding unit 12 for mixing with the host signal x. Then, watermark embedding is performed in the watermark combiner unit 14 in the above-described manner. The filter 40 shapes the noise signal such that the noise signal is perceptually masked by the host signal x. The media signal is an image signal and the model will instead be a mental-visual model of the human visual system.

By including a second signal shaping unit using the signal shaping function M2, the device according to the invention can also be modified, the signal shaping function M2 being based on the information from the filter control unit 38. The device according to this third embodiment is shown schematically in FIG. 5. The functionality of the device of FIG. 5 will be described with respect to FIG. 6, which is a flowchart of the method according to this third embodiment. In this embodiment, the noise addition is the same as the noise addition of FIG. The only difference is that the device 10 includes a second noise shaping unit 44. For example, the host signal x is first obtained (step 48) by loading the signal from the memory in which the host signal is stored (step 48), for example, the noise signal n is provided from the noise generating unit (step 50) The noise signal n is then shaped using a first noise shaping function M1 in the filter 40 to obtain a shaped noise signal n _s (step 52). Then, the shaped noise signal (n _s) is added to the host signal (x) by the first addition means 12 in order to provide a modified host signal (x + n _s) or is mixed with a host signal (Step 54 ). The combiner unit 14, which may be one of the units shown in FIG. 2 or 3, or may only be a filter, for example, receives the modified host signal x + n _s and receives the watermarked host change signal m _The watermark is combined with this signal to provide _w ) (step 56), and the watermarked host change signal is referred to as the first host change signal. Thereafter, the first host change signal m _{w is} provided to the second signal shaping unit 44, and the second signal shaping unit is configured to provide the shaped host change signal m _ws or the second host change signal. The second signal shaping function M2 determined by the filter control unit 38 is used (step 58). The second signal shaping unit 44 is also provided in the form of a filter, the coefficients of the filter being a set according to the model P described above. Function M2 ensures that there are no extra perceptible artifacts in the watermarked signal. Then, the second host change signal m _{ws is} provided to the second adding unit 36, the second adding unit receives the changed host signal x + n _s , and the watermarked host signal or watermarked These two signals are added together to provide an output media signal y (step 60). In this way, the watermark is perceptibly masked by the media signal x. It is to be noted that since the noise signal n _s is added to the media signal unperceivably, it provides a non-perceptible watermark channel.

You can change the function used. Alternatively, when the media signal is an audio signal, a so-called threshold-in-quit (TQ) function may be used instead of the functions M1 and / or M2. In this case, the noise is prefiltered so that the noise falls to the listening threshold. Similar functions may be used in image signals and / or video.

The device and method according to the third embodiment of the invention shown in FIGS. 5 and 6 have some disadvantages, in that the noise signal is added twice to the host signal. This makes the control of watermarking processing slightly unpredictable. The device for solving this problem is shown in the schematic diagram of Fig. 7, which is a fourth embodiment of the present invention. There is no first signal shaping unit in such a device. Here, the noise signal n is first provided to the scaling unit 62, which scales the noise signal by the scaling function δ. The function δ is preferably less than 1 or between 0.1 and 0.2. Then, the downscaled noise signal δ _{n is} provided to the first adding unit 12, added to the host signal x to provide the modified host signal, and the modified host signal is denoted as (x + δn). This is because the noise signal is downscaled. The modified host signal is then communicated to the combiner unit 14, which combines the watermark w in the manner previously described. An output of the combiner unit 14 is connected to a third adding unit 64, which third scaling unit also adds to the watermarked modified host signal to provide a first host change signal m _w . Receive a non-noisy signal n. The signal m _{w is} provided to a second signal shaping unit 44, which filters the first host change signal m _w according to the function M2 described previously, M2) is based on the function P of the human listening system analysis made in the filter control unit 38. The shaped signal m _ws or the second host change signal from the filter 44 is provided to the second adding unit 36 to add to the original host signal x. Thus, the filter 44 ensures that the host change signal m _w is perceptibly masked by the host signal x. In this way, all the additional signal components are inserted only in the host signal x at one point, which makes the control mechanism more predictable.

As described above, when the host or media signal has fewer frequency components, a noise signal is added to enable more secure detection of the watermark, and the frequency components are sound when the signal is an audio signal or a spatial frequency. Frequency components. However, an audio signal is not composed of only spectral sparse sounds, but can often have fewer frequency components only in some passages or sections of music. Thus, there is no need to use the above-described embodiments of the invention in some passages or sections of the entire media signal and music. Therefore, there is a need to embed a watermark in accordance with the above-described embodiments of the present invention and to embed a watermark according to known principles depending on the characteristics of the media signal.

8 shows a device providing such functionality. The device comprises a first adding unit 12, a watermark combiner unit 14 and a second adding unit 36 according to the first embodiment. The devices according to the second, third and fourth embodiments can be easily adapted for use in the device of FIG. 8 with some easy modifications. In FIG. 8, the first adding unit 12 receives the noise signal n and the host signal x, and adds each other to shape the modified host signal x + n according to the principles described above. . The output of the first adding unit 12 is connected to the watermark combiner unit 14 via a first switch 68. The host signal is also directly connected to the watermark combiner unit 14 via the second switch 70. The analysis unit 66 uses an analysis function A to analyze the frequency content of the host signal and controls the first and second switches depending on the analysis, so that the number of frequency components of the host signal x is sparse. In this case, the first switch 68 connects the first adding unit 12 to the watermark combiner unit 14, otherwise the second switch 70 sends the unchanged host signal x to the watermark combiner unit. (14). The watermark combiner unit 14 then embeds the watermark in the signal received in the manner described above, and the second adding unit 36 supplies the first host change signal m _w to provide an output signal y. Is added to the unchanged host signal x or the changed host signal x + n. The switching is preferably a soft switch function so that the switching from one signal input to the watermark combiner unit 14 to the other gradually takes place. This means that when a switch is performed from one state to another, the switch switched on so that the signal first becomes very small, attenuates or gradually increases until the full signal passes through the switch, To be done. A switched off switch gradually attenuates the signal in the same way until the switch is completely off. The total energy passed to the watermark combiner unit is substantially constant during and after switching.

It should be noted that switching is not soft or gradual, but is preferred to be soft or gradual. In the case where soft switching is not performed, it may be sufficient to provide only one switch connecting one of the modified host signal or the unchanged host signal to the watermark combiner unit 14. When a single switch is used, it is possible to provide the switch in any position, for example, to achieve switching of the appropriate signals before the first adding unit 12.

The output signal y may be provided to a storage medium of one type 72 of the CD disk shown in FIG. The output signal y may also be provided on another form of storage medium, such as a memory in a computer.

A device and method for multiply embedding additional data in a media signal when the media signal has fewer frequency components has been described. With the present invention, it is possible to embed a watermark in a media signal that is easier to detect than a general media signal having these characteristics. The second embodiment ensures that the added noise is not perceptible, and the third embodiment ensures that both the added noise and the embedded watermark are not perceptible. The fourth embodiment has the advantage of providing a more predictable control mechanism for embedding a watermark. The additional data is still detectable even if the quality of the media signal is degraded. For example, copy control or rhetorical tracking of the processed media signal is easily performed.

The invention can be modified in many ways. For example, the noise signal may be made to contain data. This can be done in a way that one arbitrary sequence can be made to indicate "0" and the other can be made to indicate "1". In this way, addition and multiplication watermarks can be integrated into a single system. As mentioned above, the watermark may be embedded in both time and frequency domains, and the media signal may be any type of media signal. The media signal may also be an audio, video or image signal. In the case of audio, the media signal may be uncompressed audio such as PCM. However, the present invention can be applied to a compressed media signal, and in the case of audio, the uncompressed media signal may be an MP3 bitstream. However, the noise must be properly converted to the bitstream at this time. Accordingly, the invention is limited only by the claims.

Claims (28)

As a method of embedding additional data w in media signal x: Obtaining a media signal x (step 48); Mixing at least one section of the media signal x with a noise signal n; n _s ; δn to provide a modified media signal x + n; x + n _s ; x + δn 54); And Combining (step 56) the additional data (w) with the modified media signal to provide a first host altered media signal (m _w ). The method of claim 1, Said combining step is performed by multiplying said modified media signal by said additional data (w). The method of claim 2, The multiplication step is performed in a time domain. The method of claim 2, The multiplication step is performed in the frequency domain. The method of claim 1, In order to provide a shaped noise signal used to provide the modified media signal x + n _s , the first signal shaping function M1 is based on a human perception model. Shaping the noise signal (step 52). The method of claim 1, Shaping the first host altered media signal m _{w with} a second signal shaping function M2 based on a human perceptual model to provide a second host altered media signal m _ws (step 58) Purchase method to include. The method of claim 1, Adding the host change media signal (m _w ; m _ws ) to the changed media signal (step 60). The method of claim 1, And adding the host change media signal (m _w ; m _ws ) to the media signal. The method of claim 1, Further comprising scaling the noise signal using a scaling factor δ prior to the mixing to provide a scaled noise signal used to provide the modified media signal x + δn. Way. 10. The method of claim 9, further comprising adding an unscaled noise signal to the first host change media signal. The method of claim 1, The additional data is a watermark (w). The method of claim 1, Analyze the media signal (A) and, for different sections of the media signal, depending on the analysis, either the section of the modified media signal (x + n) or the section of the media signal (x) And providing for combination with the data. The method of claim 12, And a switching step between the media signal and the modified media signal for combination with the additional data, wherein the switching step is preferred for graceful switching. As a method of embedding additional data w in media signal x: Obtaining a media signal x; Analyzing the media signal (A); Mixing at least one section of the media signal (x) with a noise signal (n) to provide a modified media signal (x + n); And For different sections of the media signal, depending on the analysis, comprising combining the additional data w with the modified media signal x + n or the original media signal x Way. As device 10 embedding additional data w into media signal x: A first addition that mixes at least one section of the media signal x with a noise signal n; n _s ; δn to provide an altered media signal x + n; x + n _s ; x + δn Unit 12; And Embedding unit (14) for combining said additional data (w) with said modified media signal to provide a first host altered media signal (m _w ). The method of claim 15, And the combiner unit is arranged to combine the additional data with the modified media signal through a multiplication of the modified media signal with the additional data. The method of claim 15, A first signal shaping unit arranged to shape the noise signal using a first signal shaping function M1 based on a human perceptual model P to provide a shaped noise signal used to provide the modified media signal The embedding device further comprising 40. The method of claim 15, A second signal shaping unit arranged to shape the first host change media signal with a second signal shaping function M2 based on a human perceptual model P to provide a second host change media signal m _ws ( 44) The embedding device further comprising. The method of claim 15, And a second adding unit (36) arranged to add a host change media signal to the changed media signal (x). The method of claim 15, And a second adding unit (36) arranged to add a host change media signal to the media signal (x). The method of claim 15, Further comprising a scaling unit 62 arranged to scale down the noise signal δ n prior to mixing with the media signal x to provide a scaled noise signal used to provide the modified media signal, Purchase device. The method of claim 21, And a third adding unit (64) arranged to add an unscaled noise signal to the first host change media signal. The method of claim 15, Analyze the media signal x and provide, for different sections of the media signal, the section of the modified media signal or the section of the media signal to the combiner unit 14 depending on the analysis A. And an analysis unit (66) arranged to control, wherein the combiner unit (14) combines the additional data and the section of the modified media signal or the section of the media signal. The method of claim 23, Under control of the analysis unit, further comprising at least one first switch (68) arranged to connect the media signal or the modified media signal to the combiner unit. The method of claim 24, There is a second switch 70 controlled by the analysis unit, the first switch connects the modified media signal to the combiner unit, the second switch connects the media signal to the combiner unit, And the switches are arranged to gradually switch from one state to another. As device 10 embedding additional data w into media signal x: A first addition that mixes at least one section of the media signal x with a noise signal n; n _s ; δn to provide an altered media signal x + n; x + n _s ; x + δn Unit 12; A combiner unit (14) for combining the additional data (w) with the modified media signal (x + n) or the media signal (x) to provide a first host change media signal (m _w ); And Analyze the media signal x, and for different sections of the media signal, control the provision of the modified media signal or the media signal to the combiner unit 14 depending on the analysis A Embedded device, comprising an analysis unit (66). As the media signal y: A media signal x mixed with the noise signal n; n _s ; delta n, and comprising at least one section of the modified media signal, wherein the additional data w is a modified media signal x + n; x + n _s ; x + δn). As information storage medium 72: A media signal x mixed with the noise signal n; n _s ; delta n, and comprising a media signal y comprising at least one section of the modified media signal, wherein the additional data w is Information storage medium in combination with altered media (x + n; x + n _s ; x + δn).

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